Many types of devices have been proposed which perform various driving assists by using data stored as map information as information concerning a traveling route located forward of a vehicle. However, the map information necessary for these driving assists is stored in an HDD or a DVD-ROM, and there is a large amount of the information. Therefore, in a case where a driving assist application has to read out the map information, a relatively large delay may be caused. Since the above-mentioned driving assist application is required to have the real-time property, a system allowing an efficient use of the driving assist information is necessary.
As a technique for efficiently processing such a large amount of digital data, Patent Document 1 proposes a method. In this technique, a travelable route is calculated based on a current position of a vehicle, and information concerning a map on the route is extracted and stored as information of a point on the route, and additionally the stored data is continuously updated in accordance with traveling of the vehicle, to thereby allow a relatively large amount of digital map data to be efficiently processed in an advanced driver aid application. The information on the travel route is in advance automatically extracted as common information common to all applications, and managed. Thus, it is not necessary to access a map database upon a request from the application. This makes it easy to ensure the real-time property required for the application.
If the application exists in an external device connected to a data bus in the vehicle, it is necessary to share the driving assist information via an in-vehicle LAN. In this method, delivered information is limited to information of a travelable route, and moreover is solely delivered as information that is common to all devices. This can minimize communication traffic, and thus ensure the real-time property in communications.